Sony UNA-PSTN Operating Instructions Manual page 5

For the Customers in CANADA
This Class B digital apparatus complies with Canadian ICES-003.
INDUSTRY CANADA NOTICE
This product meets the applicable Industry Canada technical
specifications.
The Ringer Equivalence Number (REN) is an indication of the maximum
number of devices allowed to be connected to a telephone interface. The
termination on an interface may consist of any combination of devices
subject only to the requirement that the sum of the RENs of all the devices
does not exceed five.
5-GB